When an image of the sun, a fluorescent light or other highly bright subjects is picked up by a digital still camera apparatus in which a solid state image sensor such as a CCD (Charge Coupled Device) is used, a bright line in strip-shape appears in the vertical direction on the picture screen. This is called the smear phenomenon. The smear phenomenon is caused such that when electric-charge generated in each photo diode (photo-electric conversion element) of the surface image pick-up device is transferred by the vertical transfer line and is read out, the electric-charge of a portion where the amount of incident light is large overflows into the vertical transfer line or the electric-charge is generated in the vertical transfer line by directly illuminating the vertical transfer line with the incident light.
In an image pick-up device control system of an electronic shutter, automatic exposure adjustment and AGC of a digital still camera, since the electric-charge generated by the smear is not contained in the electric-charge of original incident light (effective signal component), the smear is identified as a bright subject by an automatic exposure (AE) adjustment control, which causes a problem of shortage of exposure. Further, since the smear is generated regardless of a color balance of the subject by an automatic white balance (AWB) control, a color balance arithmetic error occurs and a problem of deteriorating an automatic white balance is caused depending on the smear amount. Therefore, removal of the smear data from the output data of the CCD has been attempted in order to increase the precision of the automatic exposure adjustment control and of the automatic white balance control. Conventionally, a method to obtain the smear amount from the output level of vertical OP (optical black) which is a shaded pixel region outside the effective pixel region is performed.
In a camera signal processing system, the smear phenomenon makes the quality of the camera picture signal deteriorated, and as a result, a strip-shaped line appears in the vertical direction on the screen in a monitor, which is greatly unpleasant to the eyes. Accordingly, it is necessary to remove the smear data from the output data of the CCD. Conventionally, the method to obtain the smear amount from the output level of vertical OP (optical black) which is the shaded pixel region outside the effective pixel region has been performed.
However, when the smear amount is found from the output level of vertical OP which is the shaded pixel region outside the effective pixel region, a change in dark electric-current of vertical OP, the behavior of dark noise and a defective pixel of vertical OP must be taken into consideration, for which countermeasures are difficult to be taken. Further, a circuit configuration needs to be enlarged to solve the above problems, which causes another problem of increasing the electric power consumption. Moreover, it is also difficult to detect precisely the occurrence of weak smear phenomenon which does not reach a saturation level.